1. Field of the Invention
The present invention relates in general to a mobile communication system, and more particularly to a method for formatting a signal in a mobile communication system.
2. Description of the Prior Art
A conventional method for formatting a signal in a mobile communication system will hereinafter be described with reference to FIGS. 1a and 1b. 
FIG. 1a is a view illustrating a data flow for a non-automatic repeat request (ARQ)-type radio access bearer service to which the conventional signal formatting method is applied, and FIG. 1b is a view illustrating a data flow for an ARQ-type radio access bearer service to which the conventional signal formatting method is applied.
A medium access control (MAC) sublayer of a mobile station utilizes a MAC-protocol data unit (PDU) for peer-to-peer communication with a peer MAC sublayer of a network.
The MAC-PDU contains fields necessary to the execution of a MAC function.
In radio link control-user/control plane (RLC-U/C) layers, data transferred from upper layers is segmented into payload units (PUs) and then reassembled.
The PU is defined as a unit for the resending of an ARQ-type service, and it is dimensioned to be suitable to the lowest data rate in connection.
The RLC-U/C layers append headers for segmentation information and acknowledgment information respectively to the PUs and transfer the resultant RLC-U/C PDUs to the MAC sublayer.
The MAC sublayer, in turn, appends information multiplexing headers respectively to the RLC-U/C PDUs from the RLC-U/C layers and produces the resultant MAC-PDUs.
The MAC-PDU has a size corresponding to that of a transport block to a layer 1.
On the other hand, a non-ARQ-type variable rate service, the MAC-PDU is mapped into a transport block to be transferred to the layer 1, the size of which is variable.
As a result, in the non-ARQ-type variable rate service, the MAC-PDU is variable in size. As shown in FIG. 1a, the MAC-PDU includes a plurality of MAC-service data units (SDUs).
In an ARQ-type fixed rate service, the MAC-PDU is determined in size according to the size of a transport block where the PU is fixed in size. As a result, the MAC-PDU includes only one MAC-SDU, as shown in FIG. 1b. 
As shown in FIG. 1a, a physical layer transforms one multiplexing header and one MAC-SDU or one multiplexing header and a plurality of MAC-SDUs from the MAC sublayer into a transport block with a predetermined size. Also, as shown in FIG. 1b, the physical layer transforms one multiplexing header and one MAC-SDU from the MAC sublayer into a transport block with a predetermined size. Then, the physical layer sends the resultant transport block to the network through a physical channel.
Upon receiving the transport block sent from the mobile station through the physical channel, the network performs the opposite procedure to that of the mobile station to separate the received transport block into one MAC header and one or more MAC-SDUs and perform the associated signal processing.